Attached Link: http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx

Open XP's process manager (ctrl-alt-del) and watch the memory usage of the Poser procss. Does it reach or come close to 2GB? In that case you have reached the limit of how much memory Windows XP will give to an application - the only chance you have is to trim down your scene: Smaller textures, remove unused morphs and geometry, use lower res figures where possible. There are ways to make XP give 3GB to applications, but I have never tried it. Anyone brave enough?